Saifullah Lone

Fabrication of polymeric Janus particles by droplet microfluidics

Janus particles (JPs), with their fascinating property of asymmetry, have received considerable attention in recent years in the fields of colloidal and particulate chemistry. The particles offer a range of exciting potential applications as they possess two distinctive parts with different chemistry, colors, polarities, and/or surfaces. Currently, a number of methodologies are available for the synthesis of JPs. This review presents a short description of polymeric JPs synthesized by droplet microfluidics.

Preparation and characterization of MRI-active gadolinium nanocomposite particles for neutron capture therapy

We demonstrate the synthesis and characteristics of MRI-active Gd2O3 core/SiO2 shell/poly(2-methacryloyloxyethyl phosphorylcholine) corona composite nanoparticles (Gd2O3@SiO2@PMPC NPs). The prepared NPs have a number of attractive features in cancer diagnosis and neutron capture therapy (NCT): biocompatibility, colloidal stability, low cytotoxicity, nucleus affinity, passive targeting, etc. Monodisperse and highly crystalline Gd2O3 NPs were prepared using a polyol protocol to control the average particle size and surface properties. The Gd2O3 NPs were then functionalized with SiO2 and a biomimetic layer of PMPC, to achieve reduced toxicity and enhanced nucleus affinity, for use as an MRI-active Gd-NCT agent. The size of the NPs was tailored to be from 50 to 100 nm for passive accumulation in tumor tissue through loosened capillary vessels. The morphologies and structures of Gd2O3, Gd2O3@SiO2–Br, and Gd2O3@SiO2@PMPC NPs were studied by FT-IR, XRD, HR-TEM, and TGA. In vitro cytotoxicity was investigated with three kinds of normal and cancer cells, and in vitro and in vivo MRI analyses were performed to confirm the contrast ability, accumulation, and sustentation of NPs in tumor tissues.

Photoresponsive Phase Separation of a Poly(NIPAAm-co-SPO-co-fluorophore) Random Copolymer in W/O Droplet

The photoresponsive phase separation of a poly(N-isopropylacrylamide-co-spironaphthoxazine methacryloyl-co-allyl-2-(2,6-bis((E)-4-(diphenylamino)styryl)-4H-pyran-4-ylidene)-2-cyanoacetate) random copolymer, i.e., poly(NIPAAm-co-SPO-co-fluorophore), in water-in-oil (W/O) droplets is described. The photoresponsive aqueous droplets were generated in the coflow regime of a simple tubular microfluidic device. The phase separation of the copolymer in the W/O droplets was induced by UV light at 365 nm and was affected significantly by the presence of 2,2-diethoxyacetophenone (DEAP) and sorbitan monooleate (Span 80). When the droplets were subjected to UV irradiation for more than 2 min, the phase-separated copolymer was transferred completely from the aqueous droplet to the continuous phase of hexadecane. The phase separation arises from the photoisomerization shifting the spiro to the merocyanine form of the SPO pendant group in the copolymer, which in turn reduces the hydrophilicity of the copolymer via attractive hydrogen-bonding interactions between the merocyanine group and hydrophobic additives, i.e., Span 80, DEAP, and some stable fragments derived from the photocleavage of DEAP under UV irradiation. These interactions cause the copolymer to associate with the additives and then accelerate the phase separation of the copolymer and subsequent phase transfer of copolymer aggregates. The separate effects of DEAP and Span 80 were also investigated by UV spectrophotometric analysis of the rate coefficient of the reverse transformation (merocyanine to spiro) of the photochromic monomer. We propose a mechanism of phase separation of the copolymer in the W/O droplet based on the NMR and GC-MASS analyses of DEAP.

Facile preparation of highly monodisperse poly(NIPAAm)–AuNP composite hollow microcapsules by simple tubular microfluidics

We present an easy tubular microfluidic fabrication of highly monodisperse poly(NIPAAm)–AuNP composite hollow microcapsules with pickering effect assisted impregnation of AuNPs into the walls of microcapsules via UV-induced interfacial free-radical polymerization (IFRP). We maintained an excellent control over the monodispersity and capsule size distribution and the particles showed good thermosensitivity. The microfluidic device is simple and flexible in making; therefore, it permits a tunable UV curing chamber to control the polymerization time. Additionally, we present insight into the correlation between the polymerization time and the structural transformations (breathing, buckling and creasing) in the polymeric microcapsules. The structural transformations are independent of AuNPs embedded in the polymeric shell.

Latex particle template lift-up guided gold wire-networks via evaporation lithography

We describe a hybrid methodology that combines a two dimensional (2D) monolayer of latex particles (with a pitch size down to 1 μm) prepared by horizontal dry deposition, lift-up of a 2D template onto flat surfaces and evaporation lithography to fabricate metal micro- and nano wire-networks.

Evaporative Lithography in Open Microfluidic Channel Networks

We demonstrate a direct capillary-driven method based on wetting and evaporation of various suspensions to fabricate regular two-dimensional wires in an open microfluidic channel through continuous deposition of micro- or nanoparticles under evaporative lithography, akin to the coffee-ring effect. The suspension is gently placed in a loading reservoir connected to the main open microchannel groove on a PDMS substrate. Hydrophilic conditions ensure rapid spreading of the suspension from the loading reservoir to fill the entire channel length. Evaporation during the spreading and after the channel is full increases the particle concentration toward the end of the channel. This evaporation-induced convective transport brings particles from the loading reservoir toward the channel end where this flow deposits a continuous multilayered particle structure. The particle deposition front propagates backward over the entire channel length. The final dry deposit of the particles is thereby much thicker than the initial volume fraction of the suspension. The deposition depth is characterized using a 3D imaging profiler, whereas the deposition topography is revealed using a scanning electron microscope. The patterning technology described here is robust and passive and hence operates without an external field. This work may well become a launching pad to construct low-cost and large-scale thin optoelectronic films with variable thicknesses and interspacing distances.